1. Field of the Invention
The present invention relates to novel fluorine-containing 2-nitroimidazole derivatives and a radiosensitizer comprising the same, which facilitates inactivation of intractable hypoxic cells in malignant tumors by irradiation.
2. Description of the Related Art
To suppress reproduction or growth of malignant tumor cells, radiation exposure and administration of anti-tumor compounds or immunity substances are known and actually employed independently or in combination with surgical therapy. Among them, the radiation exposure has been employed for a long time.
A hypoxic cell sensitizer (or radiosensitizer) which is a drug for increasing sensitivity of the hypoxic cells against the radiation has been developed since it is promising means for increasing effects of radiotherapy.
Hitherto, various hypoxic cell sensitizers have been developed (cf. "Gan to Kagakuryoho" (Cancers and chemotherapy), Vol. 8, No. 11, November 1981, 1659).
1-(2-Nitro-1-imidazolyl)-3-methoxy-2-propanol (Misonidazole), which is one of typical hypoxic cell sensitizers, is about twice as effective as when no Misonidazole is used. However, it is hardly administered in an effective amount since it has strong neurotoxicity. No sensitizing effect was confirmed from the results obtained by administering it in human beings (cf. Reference 4 cited in the above "Gan to Kagakuryoho").
To increase sensitizing activity of the radiation and simultaneously to decrease the neurotoxicity, nitroimidazole derivatives have been studied (cf. Japanese Patent Kokai Publication No. 12763/1987). However, the conventional derivatives have insufficient radiosensitization
It has been found that the radiosensitizing function of the azole compounds is attributed to their azole rings while the side chain contributes to their solubility in oils and pharmacological characteristics (Int. J. Radiat. Biol., 35, 1979, 151).
Compounds having a fluorine atom at a specific position in a molecule have been increasingly used as medicines because of mimic effects of the fluorine atom or modification of methabolic inhibition effect and solubility in oils (cf. "Kagaku no Ryoiki" (Chemical Fields), 35, 441 (1981)).